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The construction of ecological systems to treat acid mine water is a recently developed ameliorative technology. In a study of systems constructed prior to 1986 in the Appalachian bituminous coal region, two plants were frequently found as dominant vegetation: sphagnum (moss) and typha (cattails). Systems were designed to mimic natural ecosystems dominated by one or the other vegetation type, or a combination of the two in the same plot or sequential plots. Data analysis of individual plots indicates that systems that include both cattails and moss show the greatest difference between inflow and outflow metal and acidity concentrations. Iron, manganese, and suspended solids concentrations were lowered to the greatest extent in these systems, and ph showed the largest increase (decrease in hydrogen ion concentration). However, net acidity was higher in effluent, and sulfate concentrations were essentially unchanged. Sphagnum-dominated constructed wetland plots were noteworthy for their long turnover times (156 h) and the increased concentrations of manganese in effluent water. Typha-dominated wetland plots showed shortest turnover times (median of 19.1 H), slight modification of ph, and no impact on suspended solids load. In relation to contact time, typha systems showed the highest average concentration change per contact hour, more than 10 times that of sphagnum-dominated systems. Volume-to-flow-path-length ratios were found to be comparable for all three system vegetation types.